It is known, for example as disclosed in U.S. Pat. Nos. 2,464,890; 2,747,422; 3,632,086; 3,861,648; 3,892,141; 4,187,733 and 5,199,738, to provide two-speed jacks and/or landing gears for trailers and the like, which enable lowering of the ground engaging leg at a high gear ratio to a position adjacent the ground, and to thereafter lower the ground engaging leg at a low gear ratio providing high torque for raising the trailer to a desired support position. The two-speed jacks in the above patents, however, require the input drive to be stopped and then manually shifted from the high gear ratio to the low gear ratio drive during lowering of the ground engaging leg and similarly stopped and manually lifted from the low gear ratio drive to the high gear ratio drive during raising of the ground engaging leg.
It has also been proposed as shown in U.S. Pat. No. 2,674,438, to provide a jack having two jack screws of different pitch, with one jack screw for extending and retracting one section of the support leg at a high speed and a second jack screw for extending and retracting a second section of the support leg at a lower speed. The two jack screws are disposed in axially aligned relation and the distance through which the ground engaging leg can be extended at high speed is limited by the length of the high speed screw and the distance at which the leg can be extended at low speed, high torque is limited by the length of the low speed screw.